Studies of the effects of environmental agents on human health are a vital part of the mission of the institute. As such studies are almost always observational rather than experimental, interpretation of the data is complex. Good statistical collaboration in all phases, including conception, design, analysis, and interpretation, is essential to the success of this work. During the current year, we were active collaborators on many projects. Included were studies of the adverse effects of occupational exposure, studies of environmental causes of lung cancer, studies of effects of prenatal smoke exposure, studies of infant pain, studies of genetic damage from HIV therapy, and basic investigations of reproductive function and disorders, including fibroids and preeclampsia.